kness.

In a younger condition, before the animal has bored down to the full
depth, and whilst the cavity is only of moderate diameter, the lower
part of the peduncle, instead of being attached to the inside of a cup,
adheres to small, irregular, nearly flat, calcareous discs, overlapping
each other like tiles (figs. 1, 2 _a'_). They are placed one below the
other, generally in a straight line, and are attached firmly to one side
of the burrow. The discs are oval, or rounded, or irregular, and are
commonly from 1/20th to 1/10th of an inch across: they usually form a
quite straight ribbon, widening a little downwards: each little disc
overlaps and extends beyond the one last formed, fully half its own
diameter. I have seen one row of discs an inch in length, but the upper
discs are always worn away by the friction of the calcified serrated
scales on the peduncle. It is very important to observe that the lowest
disc is not fixed, (as was the case with the cup,) at the very bottom of
the burrow, but on one side, just above the bottom, which latter part is
occupied by the blunt basal end of the peduncle.

In a valuable paper on _L. Nicobarica_, by Reinhardt, presently to be
referred to, the disc is said to be attached on the carinal side (see
fig. 2) of the peduncle; and this, I believe, is general. I have seen
one instance in which, during the excavation of a new burrow, an old
burrow was met with, and the row of discs turned down it, making, with
their previous course, nearly a right-angle. In another similar
instance, the discs, instead of turning down, became very large and
broad, and so fairly formed a bridge across the old burrow (fig.
1),--becoming narrow again as soon as the animal recommenced burrowing
into the solid rock. Sometimes, as it appears, the animal, whilst still
small, from some unknown cause, stops burrowing downwards, and then a
cup is formed at the bottom of the hole. As soon as the animal has got
to its full depth, the burrow increases only in diameter, and during
this process the linear row of discs is ground away and lost; a cup is
then formed. The little discs can be deposited or formed only at each
fresh exuviation; and as some of the burrows are above two inches in
depth, and as on an average each disc does not extend beyond the
underlying disc more than 1/15th of an inch, an animal which has bored
two inches in depth, must have moulted at least thirty times. I may here
remark that I have reaso